Large amounts of organic solvents are used in paint factories, semiconductor factories, or printing factories. It has been known that the VOC emitted from the factories to the atmosphere influence considerably adversely on the atmospheric environment by: forming harmful organic fine particles through a reaction with solar light, ozone, and the like; increasing an ozone concentration in the atmosphere; and the like. Therefore, there has been a strong demand for collection/detoxification of the VOC.
As a method for collecting and detoxifying the VOC with a reduced energy amount, a method of desorbing and decomposing the VOC that have been absorbed by a hydrophilic zeolite by using silent discharge has been proposed. (see Patent Document 1, for example).
Also, there has been known a method including: absorbing VOC by bringing an exhaust gas containing the VOC in contact with a photocatalyst in the form of particles; and irradiating the photocatalyst with ultraviolet light while being transferred on a belt conveyer (see Patent Document 2, for example).
Patent Document 1: JP-A-2002-126445 (see FIG. 1 and pages 2 to 3)
Patent Document 2: JP-A-2002-284.45 (see FIG. 1 and pages 4 to 5)
When the VOC absorbent is in a state where absorption is saturated to fail to satisfactorily absorb the VOC in the gas, such state is called breakdown of the VOC absorbent (see Patent Document 1, for example).
In a harmful substance cracking unit using a photocatalyst, the photocatalyst in the form of fine particles is taken out from an absorbing layer and then decomposed/recovered by irradiation with ultraviolet light during the photocatalyst is transferred on a belt conveyer. In this case, since the photocatalyst is taken out from the absorbent and transferred on the belt conveyer, the photocatalyst must be in the form of the fine particles.